The present invention relates to an apparatus and method for controlling a venetian blind to allow opening one portion while closing another portion.
Venetian blinds are a well-known type of window covering which allow for selectively and gradually varying the amount of light and/or ventilation allowed to pass from a window through the blind into a room of a dwelling. Such blinds are typically constructed with a plurality of vertically spaced-apart slats which extend horizontally in parallel with one another. The slats are usually held in place by pairs of tilt strings spaced apart along the width of the blind, with a first string of each pair being disposed vertically along a front edge of the slats and a second string of each pair being disposed vertically along the back edge of the slats opposite the first string. Bridging ties extend from the first tilt string to the rear tilt string, providing a support upon which the slats rest.
Generally, a lift string is disposed vertically between the tilt strings of each pair to extend from a head rail at the top of the blind vertically downwardly to a bottom rail positioned at the bottom of the blind, to which the lift string is attached. When the free ends of the lift strings are pulled, an upward movement of the bottom rail occurs and the blind is raised upwardly relative to the window. When the tilt strings of each pair are moved vertically in opposite directions from one another, the slats are caused to rotate about their long axes to thereby vary the rotational position of the slats and thus vary the amount of light and/or ventilation allowed to pass through the blind. Control of the rotation of the slats is typically carried out by a pair of tilt cords or by a hanging tilt rod. This description is for a typical venetian blind, but there may, of course, be other styles and types of venetian blind which do not fit exactly within the above description.
Although venetian blinds are a fairly versatile window covering (because they may be operated to allow varying degrees of light and/or ventilation, as well as sight access, therethrough) it is not common with present venetian blind constructions to close only a part of the blind while allowing another part to remain open, or vice versa. While it is known in the prior art to do such (see for example U.S. Pat. No. 4,869,308 issued to Chang), design and manufacture considerations limit its feasibility in practice. More specifically, prior art methods require either an extensive modification of an existing blind or else a complicated, expensive design and manufacture process to create a new blind. Further, once these modifications or designs have been instigated, they cannot be readily reversed to allow uniform movement of all the slats.
The need for a system which can easily convert an existing venetian blind into a blind having varying slat orientation capabilities, and back again, should be apparent. For example, it may be desirable to close the upper portion of a venetian blind to maintain the incoming light at a preferred reduced level, while keeping the lower portion of the blind in an open position to allow sight access, indirect light and/or ventilation therethrough. Alternatively, it may be desirable to close the lower portion of the blind for purposes of privacy, while maintaining the upper portion of the blind in an open position to allow light, ventilation and limited sight access therethrough.